1. Field of the Invention
The present invention relates to a data recording medium and method of manufacturing the same, and more particularly, to a ferroelectric recording medium and method of manufacturing the same.
2. Description of the Related Art
As internet technology develops, demand for recording media which can record a huge amount of information such as moving pictures, in particular, portable recording media, has increased. This demand is an important factor leading the next-generation information recording media market.
Recording media which can record a huge amount of information and devices for recording and reading information in the recording medium are the most essential issues for the information recording media market.
Portable, non-volatile data recording devices are classified into solid-state memory devices, for example, flash memory, and disk type memory devices, for example, hard disks.
Since the capacity of solid-state memory devices will only increase up to several gigabites (GB) in the next several years, solid-state memory devices may not be used as large data recording devices whose capacity must be greater than several gigabites in the near future. However, solid-state memory devices may be used for high speed apparatuses such as personal computers (PC). For the time being, hard disk type memory devices may be used as a main recording apparatus.
A typical magnetic hard disk mounted in a portable apparatus will have a capacity of 10 GB in the near future, but a capacity of more than 10 GB may not be accomplished due to a superparamagnetic effect.
A memory device using a scanning probe technique for recording data and using a ferroelectric material as a recording material has been developed. When using the scanning probe technique, i.e., a scanning probe microscope (SPM) technique, an area of several to tens of nanometers can be probed by a probe. In addition, since a ferroelectric material is used as a recording medium, a superparamagnetic effect will not occur, unlike in a magnetic recording medium. The recording density in the recording device using ferroelectric material can be greater than in the magnetic recording medium.
In the recording medium using an SPM technique, recorded data are defined by the polarity of the polarization of the ferroelectric material.
Due to ferroelectric polarization, an electric field is emanating from the surface. When an appropriate probe is placed into that field, the field induces a charge depletion or accumulation region at the apex of the tip. This in turn induces a capacitance or resistance change of the probe. Depending on the polarity of the ferroelectric polarization, the resistance or capacitance is increased or decreased. Data recorded on a ferroelectric recording medium using the SPM technique can be read by measuring the change in the capacitance or resistance of the probe. Writing is done by locally changing the ferroelectric polarization of the medium. This is done by applying an electric voltage to the probe, where the voltage is high enough to induce ferroelectric switching in the medium.
As described above, a ferroelectric recording medium using an SPM can have higher data recording density than a magnetic recording medium. However, it should be considered that the region of one bit data recording is a polarized area. In order to further increase a data recording density of a ferroelectric recording medium, the size of the bit data recording region in a ferroeletric recording medium should be reduced.
However, since the reduction in the size of the bit data recording region is very much dependent on the reduction of the probe size, a further increase of the data recording density of the ferroelectric recording medium will be difficult unless epoch-making technology for reducing the probe size is developed.